Abstract
Plant growth promoting rhizobacteria and mucorrhizal fungi play an important role in the supply of nutrients in plants. These microorganisms are usually spread around rizosphere and facilitate absorbtion of nutrients In order to evaluate the effect of plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi on growth, yield, and quality traits of onion. a feild experiment in a completely randomized block design with 8 treatments and 3 replications was conducted. In this experiment onion seed (Horand landrace) was inoculated with bacteria including Azospirillum AC46I, Pseudomonas fluorescens Chao, and species Glomus intraradices of arbuscular mycorrhizal fungi. Then inoculation onion seed cultivated. The effect of treatment on TSS and potassium concentration was not significant. But leaf number, fresh weight, dry weight of onion, bulb neck diameter, harvest index, dry matter percentage, yield, phosphorous concentration, bulbing ratio and chlorophyll content were significant ( p≤1%) and dry weight shoot, bulb diameter at 5% probability level. Inoculation including the plant growth promoting rhizobacteria and mycorrhizal fungi had a higher dry matter content (10-16/24%) and phosphorus concentration (53/57%). And also the highest yield per square meter (10.33) was obtained by the combined of bacteria and fungi. Generally application of AMF with two PGPR (Pseudomonas fluorescens and Azospirillum) led to better bulb yield and quality traits of bulb in comparison with control plants and plants inoculated with individual AMF and PGPR bacteria.

Salispour M, 2003. Study of the effect of phosphate microbial fertilizers containing phosphate soluble microorganisms on quantitative and qualitative yeild of maize. Third National Conference on the Use of Bio-Life Materials and the Effective Use of Fertilizer and Poison in Agriculture. March 2-4, 2003. Tehran.